YT Embed API events implements

ytevents.js

var thePlayer = new YT.Player('yt-embed', {
          height: '360',
          width: '540',
          videoId: 'bScJ8bbwMNM',
          events: {
            'onStateChange': function(e){
                switch (e.data) {
                    case YT.PlayerState.ENDED:
                        clearWatcherVideo();
                        break;
                    case YT.PlayerState.PLAYING:
                        watcherVideo();
                        break;
                    case YT.PlayerState.PAUSED:
                        clearWatcherVideo();
                        break;
                    case YT.PlayerState.BUFFERING:

                        break;
                    case YT.PlayerState.CUED:
                        break;
                }
                
            }
          }})

function logVideoPercentual() {
    var total = thePlayer.getDuration(),
        current = thePlayer.getCurrentTime();

    console.log('percentual played', (current/total) * 100);
}

function watcherVideo () {
    window.videoInterval = setInterval(function(){
        logVideoPercentual();
    }, 1000);
}

function clearWatcherVideo() {
    clearInterval(window.videoInterval);
    logVideoPercentual();
}